Traditionally, screen doors have been made of wood or metal, such as aluminum. Wood has drawbacks, however. It must be painted or coated to protect it from the elements. If made of less expensive woods, such as pine, it may split or warp easily. It may be attacked by mold and fungus. Aluminum doors are much more expensive.
Polyvinyl chloride has been used in place of wood in siding for years. Recently, other uses of this material have been made. For example, interior shutters and parts of windows are now commonly made of vinyl. Windows and shutters, whether vinyl or wood, are made to order are made to measurements rather than custom-fitted at the job site. The dimensions of the window frame are supplied to a manufacturer who builds the shutters or windows to the measurements. These items are hollow, with walls typically less than 1/8th inch thick, to save material and decrease weight. For added strength, ribs or other interior structures are added as needed. In some cases, metal bars are used to reinforce operable, exterior shutters.
As a practical matter, screen doors cannot be made of the same materials as vinyl shutters and windows. The door needs to fit closely in a door frame that may not be rectangular or "plumb" but may lean or be narrower at the top or bottom. A screen door made of wood can be cut and trimmed on the job site. A hollow core vinyl door, on the other hand, especially one with metal reinforcing bars, could not be trimmed on the job site without the risk of cutting through the wall, generally less than 1/8 inch thick, without jeopardizing with the structural integrity and appearance of the door. Finally, shutters and windows are usually ordered in quantity, unlike screen doors. Therefore, there is little incentive to provide screen doors made to measurement.
Foamed plastics, and vinyls in particular, are sometimes used for interior ceiling and floor molding, brick molding or picture frame molding. The ends of these materials are cut to length at the job site and nailed into place. However, molding does not support weight, does not take the abuse of a screen door nor is it as complex a structure as a screed door. For example, a screen door must support the screen and hardware on a multi-component frame.
Thus, there remains a need for a screen door that does not have the disadvantages of either aluminum or wood, that can be custom fitted at the job site, unlike hollow core shutters and windows, and will take abuse.